604 THE DESCENT OF MAN, 



have been classed amongst the Quadrumana, as surely as th» 

 still more ancient progenitoi of the Old and New World monkeys. 

 The Quadrumana and all the higher mammals are probably de- 

 rived from an ancient marsupial animal, and this through a 

 long line of diversified formiS, from some amphibian-like creature, 

 and this again from som*. fish-like animal. In the dim obscurity 

 of the past we can see that the early progenitor of all the Verte- 

 brata must have been an aquatic animal, provided with branchiae, 

 with the two sexes united in the same individual, and with ths 

 most important organs of the body (such as the brain and heart) 

 imperfectly or not at all developed. This animal seems to hav« 

 been more like the larvae of the existing marine Ascidians than 

 any other known form. 



The high standard ot our intellectual powers and moral dis- 

 position is the greatest difiiculty which presents itself, after we 

 have been driven to this conclusion on the origin of man. But 

 every one who admits the principle of evolution, must see that 

 the mental powers of tks higher animals, which are the same in 

 kind with those of man, though so different in degree, are capabl* 

 of advancement. Thus the interval between the mental powers 

 of one of the higher apes and of a fish, or between those of an 

 ant and scale-insect, is immense; yet their development does not 

 offer any special difficulty; for with our domesticated animals, 

 the mental faculties are certainly variable, and the variations 

 are inherited. No one doubts that they are of the utmost im- 

 portance to animals in a state of nature. Therefore the condi- 

 tions are favorable for their development through natural selec- 

 tion. The same conclusion may be extended to man; the intel- 

 lect must have been all-important to him, even at a very remote 

 period, as enabling him to invent and use language, to make 

 weapons, tools, traps, &c., whereby with the aid of his social 

 habits, he long ago became the most dominant of all living crea- 

 tures. 



A great stride in the development of the intellect will have 

 followed, as soon as the half-art and half-instinct of language 

 came into use; for the continued use of language will have 

 reacted on the brain and produced an inherited effect; and this 

 again will have reacted on the improvement of language. As Mr. 

 Chauncey Wright^ has well remarked, the largeness of the brain 

 in man relatively to his body, compared with the lower animals, 

 may be attributed in chief part to the early use of some simple 

 form of language, — that wonderful engine which affixes signs to 

 all sorts of objects and qualities, and excites trains of thought 



' 'On the Limits of Natural Selection,' in the 'North American Re- 

 view,' Oct. 1870, p. 295. 



